Older Fentanyl Strips
Image: Rapid Response brand strips being tested in our first lab study at the University of California San Francisco, January 2017.
How to Use the Older Fentanyl Test Strips
Read this first
This page provides instructions for using the older fentanyl test strips (the blue ones), most of which are manufactured by a company called Assuretech. We no longer sell these strips because they often produce false positives with meth, MDMA and cocaine.
However, because these strips are still being sold by other companies under various brand names, we’ve written these instructions to help you use them if you still have them. It’s especially important to use the right dilutions to avoid false positives and false negatives with these strips.
If you are a nonprofit or social service agency still distributing the older strips, we can provide you with free instruction sheets. Just contact us here. Or consider buying our new, improved fentanyl test strips.
How do I know if I have the older strips?
The most popular brand of Assuretech strips are the “Rapid Response” strips sold by BTNX. They come in green packaging that looks like this:
However, there are many other companies that also sell Assuretech strips under different brand names, in different packaging. The best way to know whether you have the older strips is to look at the color of the strip itself:
- Our newer strips are yellow.
- The older strips are blue.
WARNING! If your strips do not look like either of the two strips above, do not use them! There are many companies who sell fentanyl test strips for urine testing, but those strips have not been laboratory assessed for harm reduction use.
NEW WARNING! (November 15th, 2022) We’ve recently discovered that some distributors purchase strips from multiple manufacturers and have them branded to look the same. Also, some manufacturers purchase antibodies from different antibody manufacturers. This means any given brand of strip may contain different antibodies and/or different formulations that affect their sensitivity, changing their likelihood of producing false positives and false negatives. A blue strip like the one pictured above, therefore, might not actually be manufactured by Assuretech at all, in which case the instructions below may not work.
How to use the Assuretech strips
These instructions do not apply to our new, improved fentanyl test strips. To purchase our new strips, click here.
Disclaimer
If you follow these instructions carefully, the Assuretech fentanyl test strips can detect fentanyl in most drug samples. However, they are known to produce false positives with meth and MDMA, as well as cocaine that contains levamisole or lidocaine.
WARNING! Even when using the greater dilution recommended in the instructions below, false positives can still happen with the Rapid Response strips. Recent laboratory studies have shown that these strips have a high degree of lot-to-lot variability in how they function. It is currently unknown whether this is due to poor quality control measures by Assuretech, or whether different lots of the Rapid Response brand are made by different manufacturers.
While you should never assume that a positive result is a false positive, the high number of false positives with meth, MDMA, and cocaine make the Assuretech strips less useful for testing these drugs.
No fentanyl test strip on the market can detect every fentanyl analog, and none of them can detect non-fentanyl related opioids. A negative result does not guarantee that your drug sample is free from all synthetic opioids.
The chocolate chip cookie effect
When fentanyl (or a fentanyl analog) is mixed in with heroin, cocaine, or other drugs, it is NEVER mixed evenly. Powder from one side of a baggie (or on the edge of a pressed tablet) may contain no fentanyl at all, yet powder from the other side may contain a fatal dose. This is called the “chocolate chip cookie effect” and is why it is best to test every bit of the drug you intend to consume!
We’ve also included a backup option below (the “partial test” method) that can be used in case of emergency, or if you lack the resources necessary to conduct a full test.
Test everything you intend to consume
Testing everything requires dissolving your entire dose or batch in water.
- For drugs consumed orally, you can dissolve your dose and drink the water after testing. (The strips do not contaminate the water.)
- For drugs like cocaine or meth that people like to insufflate (snort), you can get the powder back by evaporating the water. (Instructions below.)
- Dissolving your dose is a good move if you want to test your drugs right before taking them orally. Dissolving your entire batch is a good move because you can test all of your doses at once, but you’ll need to take the time to evaporate the water back out before it’s usable.
Testing a portion of your drugs
The best method is to test every bit of the drug you intend to consume, but if you can’t, at least test a good cross section. We recommend a minimum of 10 mg.
- Before doing so, crush any crystals, shards, or rocks into a fine powder.
- Next, mix the powder up as thoroughly as possible by stirring or shaking the baggie.
- This helps distribute any fentanyl that might be clumped up inside, increasing the likelihood that some will be in your sample.
Detailed instructions
STEP 1: Preparing and diluting your drugs
Whether you are testing everything you intend to consume or a smaller portion of your drugs, you need to dilute the powder in the correct amount of water.
Open the tab and follow the instructions below for each type of drug.
1. Weigh your drugs.
Use a milligram scale to get the weight of the crystals or powder you are going to test. Write it down so you don’t forget. If you don’t have a milligram scale, you can use one of our 10 mg micro scoops. 
2. Place your drugs into a small container.
- If you are testing 50 mg or less, a standard bottle cap from any 20 oz soda bottle works great.
- If you are testing more than 50mg, use a cup or bowl.
3. Add the right amount of water.
This step is very important.
FOR METH, MDMA, & COCAINE |
FOR ALL OTHER DRUGS |
| Add one teaspoon of water (5 ml) for every 10 mg of powder. | Add one teaspoon of water (5 ml) for every 50 mg of powder. |
 |
 |
Methamphetamine, MDMA, and cocaine need to be diluted more than other drugs because they can produce false positives if they are too concentrated.
While the ideal dilution for most drugs is 10 mg/ml (50 mg for every 5 ml or 1 tsp of water), meth, MDMA, and cocaine need to be diluted down to 2 mg/ml (10 mg for every 5ml or 1tsp of water).
NOTE 1: Lot-to-lot variability has shown that even this lower dilution may still produce false positives. This is why we recommend using DanceSafe fentanyl test strips. Our strips do not produce false positives at the standard dilution of 10 mg/ml for any of the most common drugs and cuts that we tested, including meth, MDMA, and cocaine.
NOTE 2: Use proper measuring spoons, like those for baking.
- 1 US teaspoon is almost exactly 5 ml
- 1 US tablespoon is three teaspoons (15 ml)
- 1 US cup is 48 teaspoons (240 ml)
If you don’t have proper measuring spoons, a standard plastic bottle cap is a bit larger than a teaspoon.
4. Stir the mixture until completely dissolved.
PROCEED TO STEP 2.
Assuretech strips cannot be used on pressed ecstasy tablets because there’s no way to know how much MDMA is present. Any results from testing pressed ecstasy pills will be unreliable. Our new DanceSafe branded strips are currently the only ones on the market that can be used on ecstasy pills.
1. Crush the entire tablet into a fine powder.
2. Pour the powder into a small cup.
3. Add approximately 12-15 ml of water (a tablespoon or quarter cup).
4. Stir the mixture. Binder may not completely dissolve. That’s ok.
PROCEED TO STEP 2.
1. Cut a small corner off the blotter.
2. Soak it in a teaspoon of water for 10 minutes.
PROCEED TO STEP 2.
If you inject drugs, you should try to test every time you inject. The easiest method is to test the residue from your spoon or cooker.
1. After preparing your shot, set the needle aside and wait to inject.
2. Add about 1 ml (1/5th of a teaspoon, or 1 cc) of clean water into the spoon or cooker.
PROCEED TO STEP 2.
STEP 2: Using the strips
After you have diluted your drug using our instructions above, it’s time to use the strips.
1. Hold the blue end of the test strip and insert the other end into the liquid.
2. Allow the liquid to travel up the strip into the test area for a full 15 seconds.
3. Remove the strip and set it down on a flat surface. Wait about three minutes.
STEP 3: Interpreting the results
One red line on top after waiting three minutes is a POSITIVE result for the presence of fentanyl. Two red lines is a NEGATIVE result.
- The lower red line may be significantly lighter than the upper red line. If you can see it at all after waiting three minutes, no matter how faint, it is still a negative result.
- No red lines (or one red line on the bottom) means the test is invalid. Usually this happens because the liquid did not travel far enough up the test strip.
IMPORTANT! Sometimes a very faint red line will initially appear in the lower area, then quickly fade away. Do NOT confuse this with a negative result. Always wait three minutes before interpreting the results.
Additional information
Fentanyl strip testing does NOT destroy your drugs.
You can get your powder back by evaporating away the water. There are many ways to do this, but one of the most popular is pouring the water into a flat-bottomed glass or ceramic dish (like a Pyrex pie dish) and heating it. Other methods involve double boilers, air evaporation (for small quantities), or even blow driers, but the most popular method is using an oven.
- Put the pan in the oven on the lowest heat setting, no higher than 225 degrees F.
- Keep the oven door cracked and keep a close eye on the pan. This process can take minutes to hours depending on how much water you’re evaporating.
- When all the water has evaporated, a film/residue will appear on the bottom of the pan. Take the pan out and let it cool.
- This residue usually looks a bit like a thin layer of ice or splotchy crystalline patterns.
- Scrape up the residue using a straight razor or other sharp tool.
- If it’s not fully dry, your powder might be a little tacky or goopy.
Don’t leave your drugs in the oven for too long after they’re dry. They won’t burn right away, but they will eventually. If your drugs weren’t brown to begin with, a tan or brown tint might mean that you’ve burned them.
Because of the risk of false positives, it is impossible to test pressed ecstasy tablets accurately with the Assuretech strips unless you know the number of milligrams of MDMA each pill contains. Most dealers don’t actually know how much MDMA is in the pills they’re selling, even if they believe they do – even labs can’t tell you “quant,” or quantification, in the U.S.
If you want to test pressed ecstasy tablets, you will need to use our new DanceSafe fentanyl test strips.
Except for suicides, overdose deaths are always accidental. The word “overdose” has sometimes carried a moral judgment that the individual was “pushing their limits” in order to get as high as possible, as if it were their own fault.
This is not true. “Overdose” simply means taking too much of a drug, and it is always accidental. Even daily opioid users who know that fentanyl is in their product have no way of knowing the amount.
Instead of blaming others, let’s work together to end accidental overdoses.
Quick reference chart
